Figure 3
![Figure 3](http://media.springernature.com/full/springer-static/image/art%3A10.1140%2Fepjqt%2Fs40507-022-00141-2/MediaObjects/40507_2022_141_Fig3_HTML.png)
Histogram of TES output voltage under weak-coherent laser illumination at \(1550~\text{nm}\) (red), \(780~\text{nm}\) (black), and \(450~\text{nm}\) (blue). The leftmost peak represents zero-photon detection. Subsequent peaks to the right represent higher photon number detections. These peaks appear at the voltage level proportional to the energy of the photons